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THE ENVIRONMENT
The observatory broadcasts on 95 MHz time signals accurate to a few micro-seconds from its Caesium beam atomic clock. The last pip of the six pip signal starts on the quarter hour. The observatory has also commissioned a new upper air sounding system. Instead of being tracked by radar the new radiosondes relay Omega navigation signals to the ground station at King's Park and a mini computer calculates the upper winds from changes in the phase of these signals.
Regular meteorological observations are made at the Royal Observatory, Kai Tak, Cheung Chau and Chek Lap Kok, by the Marine Department at Waglan Island and Green Island and by the Royal Navy at Tai O. Analyses of meteorological conditions at Chek Lap Kok are being made for the planning study for the proposed new international airport. The observatory operates more than 100 raingauges suitably sited throughout the territory. There are also 21 anemometers installed in different locations, of which 15 are operated by the Royal Observatory and six by other organisations. Winds recorded at the Star Ferry Pier, Kowloon, representing conditions in the harbour; are telemetered to the observatory. A spherics recorder is used to register thunderstorm activity within a range of about 100 km. Tide readings from gauges located at Tai Po Kau and North Point are telemetered to the observatory. These provide valuable data for warning floods during the approach of tropical cyclones. A new wave recorder installed at Waglan Island gives continuous records of wave height and period. The observatory also provides instruments for about 40 selected voluntary observing ships.
Two new acoustic radars were installed near Chek Lap Kok to investigate wind shear and turbulence in connection with the planning and design for the proposed new airport. These instruments emit sound upwards and record the echoes caused by temperature and wind irregularities in the atmosphere.
Geomagnetic observations were made in co-operation with the University of Hong Kong at Tate's Cairn and regular measurements of Beta and Gamma radioactivity are made at King's Park Meteorological Station.
A network of the three short-period seismometers at Cheung Chau, High Island and Tsim Bei Tsui are connected to a micro-computer at the Royal Observatory. The system detects earthquake tremors throughout Southeast Asia and calculates the position of the epicentres. Two earthquakes in China located by the system were felt by residents in Hong Kong in 1981. The first occurred near Hai Feng on April 9 while the second occurred near Heyuan on May 4. Long-period seismographs in a cellar beneath the observatory lawn record tremors from all over the world. The two largest earthquakes recorded were both of Magnitude 7.5 on the Richter scale; one on May 25 near the Auckland Islands and the other on September 1 near Western Somoa.